This invention pertains to the art of inflatable valves and more particularly to an inflatable valve selectively opening and closing an annular flow passage and regulating fluid flow therethrough.
The invention is particularly applicable to an inflatable valve used in biotechnological environments where cleanliness is of the utmost importance and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed in still other environments and applications.
The biotechnology industry has a number of stringent requirements particularly applicable to that field due to the nature of the products being handled. For example, chains of biological materials carried in a fluid medium are delicate and subject to severing as a result of turbulence or other rough handling. Ideally, the flow passages for handling these materials should promote laminar flow. The fluid line and any fluid handling devices such as valves, gauges, etc. preferably have smooth-walled surfaces to provide a generally constant flow area with little change in the coefficient of variation, C.sub.v. This eliminates or prevents shearing of the biological chains and also the tendency for the biological material to secure to the fluid line surfaces. Thus, it is vital that crevices, dead spaces, or other areas where the biological material may become entrapped be minimized.
Materials of construction are also limited in the biotechnological area because of the need to meet FDA approval. Stainless steel construction is preferable for many of the valve parts because of its non-reactive or inert qualities. Sealing between metal valve parts is best effected through addition of resilient or elastomeric sealing members. Incorporation of the sealing members necessarily introduces an interface area or joint between the different materials of construction. Increased emphasis must be placed on the resulting joint between valve parts to eliminate exposure of interfacing areas of the different valve part materials in order to provide a "no crevice" arrangement.
The valve structure must also be drainable, i.e., prevent pooling of dluid when the valve is not in operation. Any remaining fluid in the fluid line, particularly in the biological environment, can adversely react with the next fluid batch. The proposed valve structure must also be compatible to flow passageways of reduced size and adapted for in-line application.
Various inflatable closure devices are known in the prior art. Nevertheless, they all suffer from the problems discussed above. That is, incorporation of a flexible, inflatable member has heretofore resulted in a final structure that still has crevices formed between the inflatable member and the remainder of the valve body. Thus, although the general concept of an inflatable member to close an annular flow passage is well known, prior structures are still not adaptable to the biotechnological field where the crevices can result in adverse consequences.
French Pat. No. 1,244,750 has a flexible member, premolded before assembly to a valve body, that is mechanically secured between first and second valve body members. A nose cone includes an elongated shaft that extends through the first valve body member and the annular, premolded flexible member. The shaft is exteriorly threaded at an outer end for operative engagement with the second valve body member. This structural arrangement retains the valve body members in secure mechanical engagement and traps the flexible member therebetween. Nevertheless, crevices between the premolded flexible member and the adjacent valve body members result and are completely unsuitable for the biotechnological arrangement under consideration.
Likewise, French Pat. No. 954,333 secures a flexible band or cuff around the external surface of a valve body. This obviously does not provide a smoothwalled configuration that would promote laminar flow or inhibit entrapment of biological material. Thus, this arrangement is also deemed to be unsuitable for use in the biotechnological environment.
The valve structure should also be easily assembled to facilitate manufacture and incorporation of the valve into a pre-existing fluid line. Prior art arrangements have been quite complicated including complex valve body structures.
The present invention contemplates a new and improved valve apparatus and method of constructing same that overcomes all of the above-referred to problems and others in an economical, easily assembled structure.